CVE-2026-118175

Content of other messages could be included when replying to a crafted message

When replying to, forwarding, or editing a crafted email message as new, Thunderbird could embed parts of a different message stored in the same folder into the message being composed, without showing a blocked content warning. If the user sent the message, the content of the other message was disclosed to the recipients. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.

CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Thunderbird

CVE-2026-117867

Use-after-free in the Layout component

Use-after-free in the Layout component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 · 7.3 High EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Firefox

CVE-2026-117878

Other issue, use-after-free in the Storage: IndexedDB component

Other issue, use-after-free in the Storage: IndexedDB component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 · 6.3 Medium EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Firefox

CVE-2026-117877

Use-after-free in the Layout: Text and Fonts component

Use-after-free in the Layout: Text and Fonts component. This vulnerability was fixed in Firefox 159, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 · 6.3 Medium EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Firefox

CVE-2026-117876

Use-after-free in the Layout: Text and Fonts component

Use-after-free in the Layout: Text and Fonts component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 · 6.3 Medium EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Firefox

CVE-2026-117875

Use-after-free in the Layout: Scrolling and Overflow component

Use-after-free in the Layout: Scrolling and Overflow component. This vulnerability was fixed in Firefox 159, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 · 6.3 Medium EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Firefox

CVE-2026-117874

Use-after-free in the Internationalization component

Use-after-free in the Internationalization component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 · 6.3 Medium EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Firefox

CVE-2026-117872

Use-after-free in the JavaScript: Standard Library component

Use-after-free in the JavaScript: Standard Library component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 · 8.8 High EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Firefox

CVE-2026-117865

Use-after-free in the JavaScript: GC component

Use-after-free in the JavaScript: GC component. This vulnerability was fixed in Firefox 159, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 · 6.3 Medium EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Firefox

CVE-2026-117862

Privilege escalation due to incorrect boundary conditions in the Networking component

Privilege escalation due to incorrect boundary conditions in the Networking component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 · 9.8 Critical EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Firefox

CVE-2026-117860

Same-origin policy bypass in the DOM: Navigation component

Same-origin policy bypass in the DOM: Navigation component. This vulnerability was fixed in Firefox 159, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 · 8.1 High EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Firefox Thunderbird

CVE-2026-117889

Incorrect boundary conditions in the JavaScript Engine component

Incorrect boundary conditions in the JavaScript Engine component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 · 7.3 High EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Firefox

CVE-2026-118180

Matrix homeserver could redirect the chat session to a local file or network share

When logging in to a Matrix account, Thunderbird used the homeserver address provided in the server's login response without validating it. A malicious or compromised homeserver could provide a file: URL, causing Thunderbird to send all further Matrix requests of that session to local files or, on Windows, to an attacker-controlled network share, which could leak the user's NTLM credentials. The NTLM credential leak only affects Thunderbird on Windows. Other operating systems are unaffected. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.

CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Thunderbird

CVE-2026-118179

Request forgery via news: links

Clicking a news: or snews: link that referenced a message-ID made Thunderbird connect, without asking, to the host and port given in the link, even if it was not a configured news server. Line breaks in the message-ID were sent to the server unmodified, so a crafted link could send arbitrary commands to services reachable from the user's network. In addition, snews: links to such servers connected without TLS. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.

CVSS 3.1 · 8.8 High EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Thunderbird

CVE-2026-118177

Calendar discovery accepted local file and remote network share locations

When looking for calendars in a directory on a server, during account setup or when adding a new network calendar, Thunderbird accepted calendar locations pointing to other servers, local files or network shares. A malicious server, or a network attacker when the lookup used plain HTTP, could make Thunderbird subscribe to such a location. On Windows this could leak the user's NTLM credentials to an attacker-controlled host on every calendar refresh, and changes to the calendar could be written to the attacker's share or overwrite a local file. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.

CVSS 3.1 · 9.1 Critical EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Thunderbird

CVE-2026-118176

Bypass of remote UNC path restriction in mailbox: URLs

Thunderbird's check that prevents mailbox: URLs from accessing files on remote Windows network shares could be bypassed using extended-length UNC paths. Displaying a specially crafted email could cause Thunderbird to connect to an SMB server chosen by the attacker, disclosing the user's Windows account name and NTLM authentication data, which could be used for offline password cracking or relay attacks. This bug only affects Thunderbird on Windows. Other operating systems are unaffected. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.

CVSS 3.1 · 8.1 High EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Thunderbird

CVE-2026-118174

Displaying a message could load an attacker-chosen URL through an OpenPGP key attachment

When a message containing an OpenPGP key attachment was displayed, Thunderbird automatically loaded the attachment's content to offer importing the key. A sender could mark the attachment as an external attachment pointing to an arbitrary URL, which Thunderbird then loaded without any user interaction, bypassing remote content blocking. On Windows, a URL pointing to an attacker-controlled network share could leak the user's NTLM credentials. The NTLM credential leak only affects Thunderbird on Windows. On other operating systems, the issue allowed a remote request that bypassed remote content blocking. This vulnerability was fixed in Thunderbird 159 and Thunderbird 153.6.

CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Thunderbird

CVE-2026-117870

Use-after-free in the JavaScript Engine component

Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 · 7.3 High EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Firefox

CVE-2026-117866

Privilege escalation due to use-after-free in the Graphics: Canvas2D component

Privilege escalation due to use-after-free in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6.

CVSS 3.1 · 7.3 High EPSS < 1% KEV · Not listed

Vendors

Mozilla

Products

Firefox

CVE-2024-5700

Mozilla: Memory safety bugs fixed in Firefox 127, Firefox ESR 115.12, and Thunderbird 115.12

Memory safety bugs present in Firefox 126, Firefox ESR 115.11, and Thunderbird 115.11. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 127, Firefox ESR < 115.12, and Thunderbird < 115.12.

CVSS 3.1 · 7 High EPSS < 1% KEV · Not listed

Vendors

Mozilla Redhat

Products

Firefox Firefox Esr Thunderbird and 5 more